Place the tomatoes in the basket of a salad spinner or in a large fine mesh strainer set over a mixing bowl. Add 1 tsp salt and toss to coat the tomatoes in the salt. Let the tomatoes drain for 10 minutes. Toss the liquid.

To a small bowl, add the olive oil, Dijon mustard and a generous pinch of salt and pepper each. Whisk until smooth. Taste and adjust as needed.

To a small bowl, add chopped onion, parsley, tomatoes and vinaigrette. Toss to combine.

Best enjoyed right away. Not freezer-friendly.